Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?

Annotations only indicate readOnlyHint=false and destructiveHint=false, which align with the description. The description adds valuable behavioral context: it requires an agent API key and instructs to return the URL to the user. It implies a side effect (adding a paid site) but doesn't fully disclose what happens if the URL is not approved or if there are failures. Still, the auth requirement and the user interaction step are beyond the annotations.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Is the description appropriately sized, front-loaded, and free of redundancy?

The description is two sentences, front-loaded with the primary action. The first sentence clearly states what the tool does, the second gives usage guidance and auth requirements. Every sentence adds value; there is no filler or repetition of the tool's name.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

Given the tool's low complexity (0 parameters, no output schema), the description covers all essential aspects: purpose, usage timing, expected output (URL to return), and prerequisites (agent API key). It adequately prepares the agent to select and invoke the tool correctly, including its relationship to create_site.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

The input schema is empty (0 parameters), so there is no parameter detail to explain. The baseline for 0 params is 4, and the description doesn't need to add param semantics because none exist. It doesn't repeat any schema info, which is appropriate.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Does the description clearly state what the tool does and how it differs from similar tools?

The description clearly states the tool's function: 'Get a Stripe Checkout URL to add the first paid site to the account.' It names the specific action (get URL), the resource (Stripe Checkout URL), and the context (first paid site). It also distinguishes itself from the sibling tool create_site by explaining this is needed beforehand, so there's no ambiguity about its role.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Does the description explain when to use this tool, when not to, or what alternatives exist?

The description explicitly says when to use: 'Needed before create_site if the account has no available slot.' It also explains the expected flow: 'Return the URL to the user to approve payment.' This gives clear context and a prerequisite, effectively guiding the agent on when to invoke it relative to alternatives.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.